Method for the preparation of catalyst composition for use in cracking hydrocarbons

ABSTRACT

According to the present invention, a catalyst composition for use in cracking hydrocarbon can be prepared by spray drying an aqueous slurry containing a flash calcined alumina obtained by contacting an aluminum hydroxide with a hot air of 350°-700° C. in a short time within 5 seconds, kaolin, a precursor substance of a silica-system matrix and a crystalline aluminosilicate. Since this catalyst composition contains the flash calcined alumina and kaolin in addition to the siliceous matrix and the crystalline aluminosilicate, it can exhibit an excellent selectivity for production of intermediate fractions such as kerosene, gas oil and the like, when used for catalytic cracking of hydrocarbon.

TECHNICAL FIELD

The present invention relates to a method for the preparation of acatalyst composition for use in catalytic cracking of hydrocarbons, inparticular relates to a method for the preparation of a catalystcomposition that has a high cracking activity and can produce not only agasoline fraction but also an intermediate fraction of such as keroseneor gas oil with high yields.

BACKGROUND ART

In the catalytic cracking of hydrocarbons, as catalysts there haveusually been employed refractory inorganic oxides such assilica-alumina, silica-magnesia, silica-zirconia, alumina-boria and thelike; compositions obtained by dispersing a crystalline aluminosilicatezeolite in these inorganic oxides, and these compositions compoundedwith clay minerals such as kaolin and the like. Since the catalyticcracking of hydrocarbons is normally carried out for the main purpose ofproducing gasoline, it is preferable to use catalysts which are high incracking activity and further can obtain high octane number gasolinefractions with high yields, in other words to use catalysts which arehigh in gasoline selectivity. In view of this, catalysts have usuallybeen used by preference which are obtained by dispersing a crystallinealuminosilicate zeolite in a siliceous matrix including silica-alumina,silica-magnesia or the like.

It is said that the catalysts for use in catalytic cracking ofhydrocarbons preferably should be superior in the thermal andhydrothermal stability and attrition resistance in addition to the abovementioned cracking activity and gasoline selectivity. In the catalyticcracking process of hydrocarbons, it is common that spent catalysts areregenerated by separation of carbonaceous substances deposited thereon,and thereafter said regenerated catalysts are again available forcatalytic cracking reaction. Said regeneration treatment comprisesstripping hydrocarbons from a spent catalyst with steam, and insuccession burning off the carbonaceous deposits from the spent catalystin the presence of oxygen. Due to this, in case the catalyst is inferiorin the thermal and hydrothermal stability, the activity of the catalystis destroyed at the time of regeneration and the regenerated catalystexhibits only considerably low cracking activity and gasolineselectivity as compared with fresh catalysts. Further, because of thefact that the recent catalytic cracking, as a rule, mostly uses afluidized-bed reactor, if the catalyst is insufficient in attritionresistance, the catalyst is pulverized in the fluidized bed and lost outof the system, and this is one reason for damaging the cracking activityand gasoline selectivity of the catalyst, too.

In the light of these circumstances, the inventors of the presentapplication have previously proposed that the catalyst compositionobtained by compounding the alumina, which may be detected to becrystalline using the X-ray diffraction method, with the siliceousmatrix such as silica-alumina, and further dispersing the crystallinealuminosilicate zeolite therein is superior in cracking activity andgasoline selectivity and further exhibits excellent stability againstthermal and hydrothermal and attrition resistance (which see JapaneseLaid Open Patent Application No. 152548/1980).

The inventors of the present application have studied to improve thepreviously presented catalyst furthermore and develop a catalyst for usein catalytic cracking which may exhibit a high selectivity in thepreparation of an intermediate fraction such as kerosene, gas oil or thelike, and have discovered that a catalyst can be endowed, withoutdamaging the various characteristics of the previously proposedcatalyst, with a selectivity against the production of an intermediatefraction, by using a flash calcined alumina referred to afterwards asthe alumina which may be detected to be crystalline using the X-raydiffraction method and simultaneously mixing kaolin in the catalyst.

DISCLOSURE OF INVENTION

The method for the preparation of a catalyst for use in catalyticcracking according to the present invention is characterized byspray-drying an aqueous slurry containing a flash calcined aluminaobtained by contacting the aluminum hydroxide prepared by the Bayerprocess with a hot air of 350°-700° C. for 5 seconds; kaolin; aprecursor of a siliceous matrix; a crystalline aluminosilicate zeolite.According to the findings obtained by the inventors of the presentinvention, it has been observed that in order to improve the selectivityagainst the production of an intermediate fraction it is essential tomix both the flash calcined alumina and kaolin in the siliceous matrixwherein the crystalline aluminosilicate zeolite has been dispersed, andwhen either alone is mixed it is impossible to improve the selectivityfully to such an extent as intended initially. Although the logicalground for this is not always elucidated, it may be estimated that theuse of the flash calcined alumina in combination with kaolin may providethe catalyst with pores through which hydrocarbon molecules easilydiffuse, whereby the activity of the crystalline aluminosilicate zeolitecan be displayed to the full while preventing over-cracking ofhydrocarbon, and thus the amounts of not only gasoline fraction but alsointermediate fraction such as kerosene, gas oil or the like produced mayincrease. In this connection, it is to be noted that the catalystprepared according to the present invention is provided with poreshaving a diameter of 1000 Å-3000 Å measured by means of a porosimetermethod.

The flash calcined alumina used in the present invention can be obtainedby contacting the aluminum hydroxide (gibbsite) produced by the Bayerprocess with a hot air of 350°-700° C., preferably 550°-650° C., in ashort time for rapid dehydration. In this instance, the time requiredfor contact with the hot air is extremely important, which is normally 5seconds or less, preferably 1 second or less. This rapid dehydration isconducted so as to crack the gibbsite without destroying the hexagonallaminar crystal and thus there can be obtained a highly active alumina.In this connection, it is to be noted that this flash calcined alumina,as disclosed also in Japanese Laid Open Patent Application No.91595/1975, has been identified as being chi-alumina when measured bymeans of X-ray diffraction. The present invention employs, as apreferable kaolin, kaolinite having the same hexagonal laminar crystalas the gibbsite does.

According to the method of the present invention, the intended catalyticcracking catalyst can be obtained by preparing an aqueous slurrycontaining the above mentioned flash calcined alumina, kaolin, theprecursor of the siliceous matrix and the crystalline aluminosilicatezeolite, and spray-drying it in a conventional manner. As the precursorof the siliceous matrix, there are normally used a silicic acidsolution, silica hydrosol, silica-alumina hydrosol, silica-magnesiahydrogel and the like. Therefore, said aqueous slurry may be prepared bydispersing the flash calcined alumina, kaolin and crystallinealuminosilicate zeolite in the precursor of siliceous matrix.Preferably, the amount of the flash calcined alumina added is 10-30% ofthe final weight of the catalyst composition, the amount of the kaolinadded is 30-55% of the same, and the amount of the crystallinealuminosilicate zeolite added is 3-40% of the same.

BEST MODE OF CARRYING OUT THE INVENTION Reference Example (Preparationof the flash calcined alumina)

A flash calcined alumina was obtained by flowing the aluminum hydroxide(Al₂ O₃.3H₂ O) prepared by the Bayer process within a calcination tubewherein a hot air of 650° C. is passing through so that the contact timemay become 2 seconds. This flash calcined alumina was identified asbeing chi-alumina crystal by means of the X-ray diffraction method andwas observed to have a composition such as Al₂ O₃.0.5H₂ O.

Comparative Example 1

A water glass solution having a SiO₂ concentration of 11.2% was preparedby diluting a commercially available Water Glass No. 3. On the otherhand, an aqueous 10.5% aluminum sulfate solution was prepared. The waterglass solution and the aluminum sulfate solution were mixed continuouslyfor 10 minutes in the ratio of 20 l/min. to 10 l/min. respectively,thereby preparing a gel. This gel was aged at 65° C. for 3.5 hours andstabilized through adjusting its pH to 5.8 by addition of the waterglass. The flash calcined alumina obtained in the above ReferenceExample was mixed in this gel so that the flash calcined alumina mightbecome 20% based on the final catalyst weight, and this mixture wasspray-dried at 220° C., thereby obtaining Catalyst A.

Comparative Example 2

A gel was prepared according to the same procedure as ComparativeExample 1. This gel was divided into three parts, and one part itselfwas spray-dried to thereby obtain Catalyst B. The remaining two partswere mixed with kaolin and bentonite so as to become 20% based on thefinal catalyst weight respectively, and were spray-dried to obtaincatalysts. The kaolin-containing catalyst was named Catalyst C, and thebentonite-containing catalyst was named Catalyst D.

Example 1

A commercially available Water Glass No. 3 was diluted to prepare awater glass solution having a SiO₂ concentration of 12.73%. Separately,a sulfuric acid having a concentration of 25% was prepared. This waterglass solution and the sulfuric acid were mixed continuously for 10minutes in the ratio of 20 l/min. to 5.65 l/min. respectively, therebypreparing a silica hydrosol. This silica hydrosol was divided into twoparts. The one part was mixed with kaolin and the flash calcined aluminaobtained in Reference Example so that each weight might become 55% and10% respectively based on the final catalyst weight and further wasmixed with an aqueous slurry of a rare earth exchanged zeolite Y whoseconcentration had previously been made 30% so that the content ofzeolite might become 15% based on the final catalyst weight. Thismixture was spray-dried in a hot air at a temperature of 220° C., andthereafter was washed and dried to obtain Catalyst E.

The other one part of the above mentioned silica hydrosol was mixed withkaolin and the flash calcined alumina so that each weight might become45% and 20% respectively based on the final catalyst weight and furtheradded with the same zeolite as in Catalyst E. This mixture wasspray-dried to obtain Catalyst F.

Comparative Example 3

A silica hydrosol prepared according to the same procedure as Example 1was added with kaolin so that the amount of it contained in the finalcatalyst might become 65%, by weight and further added with the aqueoussuspension of the rare earth exchanged zeolite Y whose concentration hadpreviously been made 30% so that the content of said zeolite in thefinal catalyst might become 15% by weight. The resulting mixture wasspray-dried, and thereafter washed and dried to prepare Catalyst G.

Example 2

A silica hydrosol was prepared according to the same procedure asExample 1. Apart from this, a hydrogen type zeolite was prepared bysubjecting a sodium type faujasite to ammonium ion-exchange in aconventional manner, calcining the same at 550° C. for 3 hours, furthersubjecting this calcined matter to ammonium ion-exchange, and thencalcining this as-wet again at 600° C. for 3 hours. The above mentionedsilica hydrosol was divided into two parts. The one part was mixed withkaolin and the flash calcined alumina of Reference Example so that eachweight might become 50% and 10% respectively in the final catalyst. Thismixture was further mixed with the aqueous suspension of the abovementioned hydrogen type zeolite whose concentration had previously beenmade 30% so that the content of zeolite in the final catalyst might be20% by weight. This mixture was spray-dried in a hot wind at atemperature of 220° C., thereafter was washed and then dried to therebyobtain Catalyst H. By the use of the remaining one silica hydrosol andaccording to the same procedure, there was prepared Catalyst I whereinthe contents of kaolin, flash calcined alumina and zeolite were 40%, 20%and 20% respectively based on the weight of final catalyst.

Comparative Example 4

A mixture was prepared wherein kaolin was added in the silica hydrosolprepared by repeating the same procedure as Example 1 so that the amountof kaolin in the final catalyst might become 60% by weight and theaqueous suspension of the same kind of hydrogen type zeolite as used inExample 2 was added in said silica hydrosol so that the content of thezeolite in the final catalyst might become 20% by weight. The resultingmixture was spray-dried and thereafter it was washed and dried toprepare Catalyst J.

Comparative Example 5

A silica hydrosol prepared by repeating the same procedure as Example 1was added with the flash calcined alumina of Reference Example so thatits weight in the final catalyst might become 60% and further was addedwith the aqueous suspension of the same kind of hydrogen-type zeolite asused in Example 2 so that the content of said zeolite in the finalcatalyst might be 20% by weight. The resulting mixture was spray-dried,washed and then dried to prepare Catalyst K.

Example 3

A solution was prepared by adding 2086 g of sodium aluminate (Al₂ O₃content: 22%, Na₂ O content: 17.4%) and 958 g of sodium hydroxide (Na₂ Ocontent: 37.8%) in 1550 cc. of water while stirring. 7176 g of silicasol (SiO₂ content: 30%) having a silica particle diameter of 50 Å-500 Åwas added to this solution while stirring, and thereafter was keptstanding at room temperature for 20 hours without stirring. Next, thismixture was heated in a water bath of 95° C. for 2 hours, and then thismixture was taken out of the water bath and cooled to the roomtemperature to obtain a slurry. 1345 g of silica sol (SiO₂ content: 30%)was added to the thus obtained slurry again with stirring, and thismixture was heated in a water bath of 95° C. for 10 days and wassubjected to a filtration to remove a solid matter therefrom. Theobtained solid matter was confirmed to be a high purity faujasite bymeans of the X-ray diffraction method. The surface area of this solidmatter was measured to be 685 m² /g by means of B.E.T. method and theoxide molar ratio of said faujasite was chemically analyzed as shownbelow:

    1.02Na.sub.2 O.Al.sub.2 O.sub.3.5.5SiO.sub.2.9.2H.sub.2 O

This sodium-type faujasite was subjected to ammonium ion-exchange in aconventional manner and thereafter was calcined at 550° C. for 3 hours.The obtained calcined matter was subjected to ammonium ion-exchangeagain and then calcining this as-wet again at 600° C. for 3 hours tothereby obtain a hydrogen-type zeolite.

Then, a silica hydrosol prepared according to the same procedure asExample 1 was added with kaolin so that its weight in the final catalystcomposition might become 50%, was further added with the flash calcinedalumina of Reference Example so that its weight in the final catalystcomposition might become 10%, and was still further added with a 30%slurry of the above mentioned hydrogen-type zeolite so that the contentof said zeolite in the final catalyst composition might become 20% byweight. The thus obtained mixture was spray-dried, washed and driedagain to obtain Catalyst L.

Comparative Example 6

A silica hydrosol prepared by the same procedure as Example 1 was addedwith kaolin so that its weight in the final catalyst composition mightbecome 55%, and was added with the flash calcined alumina of Referencealumina so that its weight in the final catalyst composition mightbecome 5%, and was added further with the same kind of hydrogen-typezeolite slurry as used in Example 2 so that the content of zeolite inthe final catalyst composition might become 20 wt%. The thus obtainedmixture was spray-dried, washed and dried again to obtain Catalyst M.

Comparative Example 7

A silica hydrosol prepared by the same procedure as Example 1 was addedwith kaolin so that its weight in the final catalyst composition mightbecome 20%, and was added with the flash calcined alumina of ReferenceExample so that its weight in the final catalyst composition mightbecome 40%, and was added further with the same kind of hydrogen-typezeolite slurry as used in Example 2 so that the content of zeolite inthe final catalyst composition might become 20% by weight. This mixturewas spray-dried, washed and dried again to obtain Catalyst N.

Comparative Example 8

Catalyst O was obtained according to the exactly same procedure asExample 3 except that the flash calcined alumina of the presentinvention was replaced by an alumina having a composition Al₂ O₃.0.1H₂ Oobtained by calcining the aluminum hydroxide (Al₂ O₃.3H₂ O) prepared bythe Bayer process at 850° C. for 10 seconds.

Catalytic Performance Test Example 1

Each of the catalysts A-O obtained according to the above mentionedComparative Examples and Examples was tested with reference to itsstability against heat and steam and with reference to its crackingactivity. Said stability test was conducted in the manner of treatingthe catalyst at 760° C. for 12 hours in the air current containing 55%of steam; thereafter calcining said catalyst at 600° C. for 2 hours tomeasure its surface area and pore volume. The stability was evaluated interms of the residual ratios which were calculated by dividing thevalues of surface area and pore volume of the catalyst subjected to thestability test by the values of surface area and pore volume of thecatalyst before undergoing said steam treatment and heat treatment.While, the activity of the catalyst was tested after subjecting thecatalyst to steam and heat treatments as done in the case of thestability test. Clark oil was used as feed oil. The reaction conditionsemployed herein were as follows: reactor temperature=492° C., WHSV=8hr⁻¹, weight ratio of catalyst/feed oil=5. The obtained results areshown in Table-1 together with the compositions of the respectivecatalysts.

As is evident from Table-1, Catalysts E, F, H, I and L of the presentinvention are high in the ratio of L.C.O/H.C.O as compared with theother catalysts. This fact elucidates that these catalysts can exhibitthe excellent selectivity for production of intermediate fractions. Inthis connection, it is to be noted that although Catalysts K and N arealso high in the ratio of L.C.O/H.C.O, the amounts of coke produced areconsiderably larger than the catalysts of the present invention.

                  TABLE 1    ______________________________________    Catalyst        A      B       C    D    E    ______________________________________    Siliceous matrix wt %                    SiO.sub.2 Al.sub.2 O.sub.3                                     SiO.sub.2                  80   100     80     80   20    Compound-            Flash calcined                        20     --    --   --   10    ing agent            alumina    wt %    Kaolin      --     --    20   --   55            Bentonite   --     --    --   20   --    Zeolite Type                               RE-Y            Mixed amount                        --     --    --   --   15            wt %    Surface area BET m.sup.2 /g    Pore volume H.sub.2 O ml/g    Attrition resistance                    0.16   0.18    0.19 0.19 0.12    wt %/hr    Thermal and hydrothermal stability test    Surface area    46     39      43   40   60    residual ratio %    Pore volume     84     75      78   75   83    residual ratio %    Cracking test results    Conversion vol %                    53     51      50   49   73.3    Hydrogen wt %   0.05   0.04    0.04 0.04 0.09    .sup.(1) C.sub.5.sup. +  gasoline wt %                    36     33      35   34   48.6    Coke wt %       3.8    4.5     3.6  3.5  3.1    .sup.(2) L.C.O vol %                    29     24      25   25   20.5    .sup.(3) H.C.O vol %                    18     25      25   26   6.2    L.C.O/H.C.O vol %/vol %                    1.61   0.96    1.00 0.96 3.31    ______________________________________    Catalyst        F       G       H    I    J    ______________________________________    Siliceous matrix wt %                    SiO.sub.2                  20    20      20     20   20    Compound-            Flash calcined                        20      --    10   20   --    ing agent            alumina    wt %    Kaolin      45      65    50   40   60            Bentonite   --      --    --   --   --    Zeolite Type        RE-Y    RE-Y  H-Y  H-Y  H-Y            Mixed amount                        15      15    20   20   20            wt %    Surface area BET m.sup.2 /g     152  170  128    Pore volume H.sub.2 O ml/g      0.21 0.24 0.16    Attrition resistance                    0.13    0.10    0.09 0.10 0.10    wt %/hr    Thermal and hydrothermal stability test    Surface area    62      53      63   65   51    residual ratio %    Pore volume     85      74      80   89   72    residual ratio %    Cracking test results    Conversion vol %                    75.0    67.8    74.9 76.2 65.2    Hydrogen wt %   0.11    0.11    0.08 0.11 0.09    .sup.(1) C.sub.5.sup.+  gasoline wt %                    50.1    45.0    54.6 54.8 46.1    Coke wt %       3.1     3.0     2.8  2.9  2.6    .sup.(2) L.C.O vol %                    19.5    20.7    19.8 19.8 21.4    .sup.(3) H.C.O vol %                    5.5     11.5    5.3  5.0  13.4    L.C.O/H.C.O vol %/vol %                    3.55    1.80    3.74 3.96 1.60    ______________________________________    Catalyst        K      L       M    N    O    ______________________________________    Siliceous matrix wt %                    SiO.sub.2                  20   20      20     20   20    Compound-            Flash calcined                        60     10     5   40   .sup.   10.sup.(4)    ing agent            alumina    wt %    Kaolin      --     50    55   20   50            Bentonite   --     --    --   --   --    Zeolite Type        H-Y    H-Y   H-Y  H-Y  H-Y            Mixed amount                        20     20    20   20   20            wt %    Surface area BET m.sup.2 /g                    226    172     131  215  143    Pore volume H.sub.2 O ml/g                    0.28   0.23    0.17 0.27 0.19    Attrition resistance                    0.14   0.09    0.10 0.14 0.10    wt %/hr    Thermal and hydrothermal stability test    Surface area    68     67      53   67   52    residual ratio %    Pore volume     91     88      75   90   75    residual ratio %    Cracking test results    Conversion vol %                    81.2   79.5    66.7 80.8 66.3    Hydrogen wt %   0.16   0.09    0.09 0.16 0.08    .sup.(1) C.sub.5.sup.+  gasoline wt %                    51.2   55.1    47.2 51.0 48.0    Coke wt %       4.2    2.7     2.7  4.1  2.6    .sup.(2) L.C.O vol %                    14.8   16.0    23.4 15.2 21.9    .sup.(3) H.C.O vol %                    4.0    4.5     9.9  4.0  11.8    L.C.O/H.C.O vol %/vol %                    3.70   3.56    2.36 3.80 1.85    ______________________________________     .sup.(1) C.sub.5.sup.+ gasoline: Boiling point range C.sub.5204° C     .sup.(2) L.C.O: Boiling point range 204° C.-350° C.     .sup.(3) H.C.O: Boiling point range 350° C. or more     .sup.(4) Matter prepared by calcinining the aluminum hydroxide obtained b     the Bayer process at 850° C. for 10 seconds.

Catalytic Performance Test Example 2

The cracking activity of each of Catalyst J and H was evaluated relativeto WHSV. Both catalysts were subjected to the same pre-treatment as TestExample 1 and measured with reference to the cracking activity accordingto the exactly same reaction conditions as Test Example 1 except forchange in WHSV. The obtained results are shown in Table-2. As is evidentfrom Table-2, it is observed that Catalyst H of the present inventionexhibits a high selectivity concerning the production of an intermediatefraction, even when the conversion increases or decreases depending uponchanges in WHSV.

                  TABLE 2    ______________________________________    Catalyst   J             H    WHSV hr.sup.-1               4  8  12   16     4    8    12   16    ______________________________________    Crack-          Conver-  69.3 65.2 60.7                              57.2 78.1 74.9 70.7 67.1    ing   sion    test  vol %    results          Hydro-   0.11 0.09 0.09                              0.07 0.10 0.08 0.07 0.07          gen          wt %          C.sub.5.sup.+                   48.3 46.1 43.5                              41.9 54.2 54.6 52.6 50.4          gasoline          Coke      3.1  2.6  2.3                               2.2  3.4  2.8  2.6  2.5          L.C.O    20.1 21.4 23.0                              23.7 17.3 19.8 21.8 23.8          H.C.O    10.6 13.4 16.3                              19.1  4.6  5.3  7.5  9.1          L.C.O/   1.90 1.60 1.41                              1.24 3.76 3.74 2.91 2.62          H.C.O          vol %/          vol %    ______________________________________

What is claimed is:
 1. A method for preparing a catalyst composition forcracking hydrocarbons, which consists essentially of:spray drying anaqueous slurry containing(i) flash calcined alumina particles which havebeen prepared by contacting aluminum hydroxide which has been made bythe Bayer process, with hot air having a temperature in the range of350° to 700° C., for 5 seconds or less, (ii) kaolin, (iii) a precursorof a siliceous inorganic oxide matrix, and (iv) a crystallinealuminosilicate zeolite, to obtain catalyst particles consistingessentially of from 10 to 30 wt.% of said flash-calcined alumina, from30 to 55 wt.% of said kaolin, from 3 to 40 wt.% of said crystallinealuminosilicate zeolite and the balance is said siliceous inorganicoxide matrix.
 2. A method according to claim 1 wherein said siliceousmatrix is silica.
 3. A method according to claim 1 wherein the siliceousmatrix is a silica-alumina.
 4. A method according to claim 1 whereinboth of said flash calcined alumina and said kaolin have a hexagonallaminar crystal structure.
 5. A method according to claim 1 wherein thecatalyst particles have pores of a diameter of from 1000 to 3000Angstrom units, as measured by a porosimeter.
 6. A method according toclaim 1 in which said zeolite is rare earth exchange zeolite Y orhydrogen exchanged zeolite Y.
 7. A method according to claim 1 in whichsaid flash calcined alumina particles are chi-alumina particles.